re: Tahiti, Cook Islands, or Hawaii for Honeymoon?

Bora Bora would be the best and you can do it for a lot cheaper than most realize. If you join the Intercontinental Ambassador program you get a 2 for 1 night weekend certificate to use at any IC property. Also IHG has two resorts in Bora Bora, the Le Moana resort and Thalasso Resort. I think the Thalasso is all Over the Water Bungalows.

Another trick that you can use with IHG is to reserve a 15k point a night room anywhere for points + $70 cash then cancel the reservation so that you will get the 10k in points back almost immediately. Currently 50k is the top redemption level for IHG properties so by doing this you can basically stay at any property for at most $350/ night even a resort like Thalasso that runs $900+ per night. Also only the first level or two of rooms is usually available for awards nights, thats why it would better to look into Thalasso than Le Moana where you would have to hope that they upgrade you as an Ambassodor to over the water on a reward night.

ETA: Flights there are still going to be really expensive, I haven't figured how to significantly reduce that yet.